bool _clampProjectionMatrix(matrix_type& projection, double& znear, double& zfar, value_type nearFarRatio)
{
double epsilon = 1e-6;
if (zfar<znear-epsilon)
{
OSG_INFO<<"_clampProjectionMatrix not applied, invalid depth range, znear = "<<znear<<" zfar = "<<zfar<<std::endl;
return false;
}
if (zfar<znear+epsilon)
{
// znear and zfar are too close together and could cause divide by zero problems
// late on in the clamping code, so move the znear and zfar apart.
double average = (znear+zfar)*0.5;
znear = average-epsilon;
zfar = average+epsilon;
// OSG_INFO << "_clampProjectionMatrix widening znear and zfar to "<<znear<<" "<<zfar<<std::endl;
}
if (fabs(projection(0,3))<epsilon && fabs(projection(1,3))<epsilon && fabs(projection(2,3))<epsilon )
{
// OSG_INFO << "Orthographic matrix before clamping"<<projection<<std::endl;
value_type delta_span = (zfar-znear)*0.02;
if (delta_span<1.0) delta_span = 1.0;
value_type desired_znear = znear - delta_span;
value_type desired_zfar = zfar + delta_span;
// assign the clamped values back to the computed values.
znear = desired_znear;
zfar = desired_zfar;
projection(2,2)=-2.0f/(desired_zfar-desired_znear);
projection(3,2)=-(desired_zfar+desired_znear)/(desired_zfar-desired_znear);
// OSG_INFO << "Orthographic matrix after clamping "<<projection<<std::endl;
}
else
{
// OSG_INFO << "Persepective matrix before clamping"<<projection<<std::endl;
//std::cout << "_computed_znear"<<_computed_znear<<std::endl;
//std::cout << "_computed_zfar"<<_computed_zfar<<std::endl;
value_type zfarPushRatio = 1.02;
value_type znearPullRatio = 0.98;
//znearPullRatio = 0.99;
value_type desired_znear = znear * znearPullRatio;
value_type desired_zfar = zfar * zfarPushRatio;
// near plane clamping.
double min_near_plane = zfar*nearFarRatio;
if (desired_znear<min_near_plane) desired_znear=min_near_plane;
// assign the clamped values back to the computed values.
znear = desired_znear;
zfar = desired_zfar;
value_type trans_near_plane = (-desired_znear*projection(2,2)+projection(3,2))/(-desired_znear*projection(2,3)+projection(3,3));
value_type trans_far_plane = (-desired_zfar*projection(2,2)+projection(3,2))/(-desired_zfar*projection(2,3)+projection(3,3));
value_type ratio = fabs(2.0/(trans_near_plane-trans_far_plane));
value_type center = -(trans_near_plane+trans_far_plane)/2.0;
projection.postMult(osg::Matrix(1.0f,0.0f,0.0f,0.0f,
0.0f,1.0f,0.0f,0.0f,
0.0f,0.0f,ratio,0.0f,
0.0f,0.0f,center*ratio,1.0f));
// OSG_INFO << "Persepective matrix after clamping"<<projection<<std::endl;
}
return true;
}
